Numerous recombinant expression systems are available for production of foreign proteins. See for example Ausubel et al. (Eds.), Current Protocols in Molecular Biology, Wiley, NY (1999); Wu, R. (Ed.), Recombinant DNA methodology TI, Academic Press, NY (1995). One problem common to the available expression systems is that it is difficult to efficiently express many foreign proteins in active form at high levels. Another difficulty arises when the expression of the protein of interest leads to precipitation of the protein as an insoluble amorphous mass in the host cell bearing the expression vector. There remains a need for an efficient expression system, especially for proteins that are difficult to express. Optimally, the expression system should provide high levels of soluble, correctly folded, or active recombinant peptides or proteins that may be easily purified from the expression system.